1. Field of the Invention
The present invention relates to an improvement in a torque converter, comprising a pump impeller connected to a driving shaft, a turbine impeller connected to a turbine shaft, a stator impeller disposed between the pump impeller and the turbine impeller, and a free wheel which is interposed between the stator impeller and a stationary structure and operable to lock the stator impeller in order to allow the stator impeller to bear a reaction force generated with the amplification of torque between the pump and turbine impellers.
2. Description of the Related Art
In such a conventional torque converter, a cylindrical stationary shaft is disposed on an outer periphery of a turbine shaft and surrounded by a boss of a stator impeller, and a free wheel is interposed between the stationary shaft and the boss of the stator impeller, as disclosed in Japanese Patent Publication No.7-33861, for example.
In the torque converter including the free wheel interposed between the boss of the stator impeller and the cylindrical stationary shaft surrounded by the boss, the following problem is encountered: the size of the diameter of the stator impeller and thus, the diameter of the entire torque converter, is necessarily increased due to the concentric disposition of the stator impeller and the free wheel.
Accordingly, it is an object of the present invention to provide a torque converter of the above-described type, wherein a reduction of the diameter of the entire torque converter can be achieved, despite of the presence of the free wheel.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a torque converter comprising a pump impeller connected to a driving shaft, a turbine impeller connected to a turbine shaft, a stator impeller disposed between the pump impeller and the turbine impeller, and a free wheel which is interposed between the stator impeller and a stationary structure and operable to lock the stator impeller in order to allow the stator impeller to bear a reaction force generated with the amplification of torque between the pump and turbine impellers, wherein the stator shaft connected to the stator impeller is disposed with a tip end thereof being passed through the turbine shaft to protrude outside the turbine shaft, the tip end of the stator shaft being connected to the stationary structure through the free wheel.
The stationary structure and the driving shaft correspond to a crankcase 1 and a crankshaft 2 in each of embodiments of the present invention, respectively, which will be described hereinafter.
With the first feature, the tip end of the stator shaft passed through the turbine shaft to protrude outside of the turbine shaft is connected to the stationary structure. Therefore, the stator shaft may be merely connected to the stator impeller and hence, it is possible to reduce the diameter of the stator impeller and thus, the diameter of the entire torque converter, irrespective of the presence of the free wheel. Moreover, in a coupled state in which the stator impeller is rotated along with the pump impeller and the turbine impeller, the stator shaft connected to the stator impeller is rotated at substantially the same speed as the driving shaft and the turbine shaft. Therefore, a difference in relative rotational speeds between adjacent ones of the driving shaft, the turbine shaft and the stator shaft is extremely small and hence, the load of each of bearings for these shafts is alleviated, whereby an enhancement in durability thereof can also be provided.
According to a second aspect and feature of the present invention, in addition to the first feature, the turbine impeller is disposed at a location displaced from the pump impeller toward a case carrying the driving shaft; the turbine shaft protruding toward the case is secured to the turbine impeller; the free wheel is interposed between the tip end of the stator shaft passed through the turbine shaft and the case; and the turbine shaft is provided with a driving gear of a primary reducing device, which connects the turbine shaft and an input shaft of a transmission to each other between the turbine impeller and the free wheel.
With the second feature, the driving gear of the primary reducing device can be disposed as close to the case as possible, while avoiding an interference with the free wheel. Therefore, during operation of the primary reducing device, it is possible to suppress a bending moment exerted to the driving shaft by the driving gear to a small level to enhance the durability of the driving shaft.
According to a third aspect and feature of the present invention, in addition to the first or second feature, the stator shaft is relatively rotatably carried on the driving shaft, and the free wheel comprises an outer race formed at the tip end of the stator shaft, an inner race relatively rotatably carried on the driving shaft and non-rotatably connected to the case, and a sprag interposed between both of the races.
With the third feature, both of the outer race and the inner race are carried on the driving shaft. Therefore, a high accuracy of concentricity can be provided to the outer and inner races, whereby the operation of the free wheel can always be stabilized.
According to a fourth aspect and feature of the present invention, in addition to the first feature, the pump impeller has a boss carried on the driving shaft with a first bearing interposed therebetween; the stator shaft leading to a boss of the stator impeller is disposed concentrically around an outer periphery of the driving shaft; the turbine impeller has a boss carried on the stator shaft with a second bearing interposed therebetween, and an operating oil is supplied into an oil chamber defined between the pump impeller and the turbine impeller through between the first and second bearings; and the first and second bearings are provided with bi-directional seal means for inhibiting the passing of a fluid such as air from any of the inside and outside of the bearings.
With the fourth feature, the bi-directional seal means inhibits the passing of fluid such as air to each of the bearings from any of the inside and outside of each bearing. Therefore, when the hydraulic pressure supplied to the torque converter is low, it is possible to inhibit the outside air from entering the inside of the torque converter through the first and second bearings, despite the acceleration of the rotation of the pump impeller, thereby preventing a reduction in transmitting efficiency due to the incorporation of the air into the operating oil. When the hydraulic pressure supplied to the torque converter is raised, such hydraulic pressure can be inhibited from leaking to the outside through the first and second bearings, thereby maintaining the internal hydraulic pressure in the torque converter at a high level to enhance the transmitting efficiency. Thus, it is possible to ensure a high transmitting efficiency, irrespective of the level of the hydraulic pressure supplied.
According to a fifth aspect and feature of the present invention, in addition to the first feature, the pump impeller and the turbine impeller have core rings relatively rotatably lapped on a core ring of the stator impeller, and a lap gap g between adjacent ones of the core rings and an inner circumferential radius R of the core ring of the stator impeller are set to have a relation of g/Rxe2x89xa61.0%.
With the fifth feature, when the oil within the torque converter is passed from the turbine impeller through the stator impeller toward the pump impeller during the amplification of torque, a relatively large difference in pressure is generated between an inlet and an outlet of the stator impeller. However, the lap gap between adjacent ones of the core rings exhibits a large throttling resistance under the establishment of g/Rxe2x89xa61.0% and hence, it is possible to effectively inhibit the flowing-out of the oil from the turbine impeller into an in-core oil chamber and the flowing-in of the oil from the in-core oil chamber into the pump impeller, thereby effectively preventing reductions in transmitting efficiency and torque ratio in the torque converter.
According to a sixth aspect and feature of the present invention, in addition to the first feature, the pump impeller and the turbine impeller have core rings relatively rotatably lapped on a core ring of the stator impeller, and a lap margin A between adjacent ones of the core rings and an axial maximum width W of the stator impeller are set to have a relation of A/Wxe2x89xa77.5%.
With the sixth feature, a large throttling resistance can be provided to the lap gap between adjacent ones of the core rings under the establishment of A/Wxe2x89xa77.5% and hence, it is possible to effectively inhibit the flowing-out and flowing-in of the oil to effectively prevent reductions in transmitting efficiency and torque ratio in the torque converter.
According to a seventh aspect and feature of the present invention, in addition to the first feature, the pump impeller and the turbine impeller have core rings relatively rotatably lapped on a core ring of the stator impeller, and an annular seal member is interposed between opposed surfaces of adjacent ones of the core rings.
With the seventh feature, the lap gap between adjacent ones of the core rings is sealed by the annular seal member. Therefore, it is possible to reliably inhibit the flowing-out and flowing-in of the oil through the gaps, thereby reliably preventing reductions in transmitting efficiency and torque ratio in the torque converter.
According to an eighth aspect and feature of the present invention, in addition to the first feature, the pump impeller and the turbine impeller have bosses opposed to opposite sides of a boss of the stator impeller; a supply oil passage leading to an oil pump is provided to communicate with an inner periphery of the boss of the stator impeller; an oil outlet is provided in an oil chamber defined behind the turbine impeller to communicate between the pump impeller and the turbine impeller; a gap between the bosses of the turbine impeller and the stator impeller is substantially closed; and an oil inlet is provided in at least one of the bosses of the pump impeller and the stator impeller to permit the inner periphery of the boss of the stator impeller to communicate with an outlet of the stator impeller.
With the eighth feature, when there is a large difference in pressure generated between the inlet and outlet of the stator impeller, even if the pressure discharged from the oil pump is dropped remarkably, the entire amount of the oil discharged by the oil pump is supplied through the oil inlet to the outlet of the stator impeller. Thus, it is possible to effectively inhibit a reduction in pressure in such outlet and to prevent the generation of bubbles in the oil. On the other hand, the oil exiting the turbine impeller cannot flow out between the bosses of the turbine impeller and the stator impeller, and the entire amount of such oil can be passed through the stator impeller. Thus, reductions in torque ratio and transmitting efficiency are inhibited.
According to a ninth aspect and feature of the present invention, in addition to the eighth feature, the oil inlet is comprised of a gap between the bosses of the pump impeller and the stator impeller, which gap is larger than the throttled gap between the bosses of the turbine impeller and the stator impeller.
With the ninth feature, it is possible to contribute to preventing reductions in torque ratio and transmitting efficiency by a simple arrangement.
According to a tenth aspect and feature of the present invention, in addition to the eighth feature, the oil inlet is comprised of a radial groove defined in at least one of opposed surfaces of the bosses of the pump impeller and the stator impeller.
Even with the tenth feature, it is possible to simplify the arrangement and prevent reductions in torque ratio and transmitting efficiency.
According to an eleventh aspect and feature of the present invention, in addition to the eighth feature, the oil inlet is comprised of a through-bore provided in the e boss of the pump impeller.
Even with the eleventh feature, it is possible to simplify the arrangement and prevent reductions in torque ratio and transmitting efficiency.
According to a twelfth aspect and feature of the present invention, in addition to any of the eighth to eleventh features, an annular seal member is interposed between opposed surfaces of the boss of the turbine impeller and the stator impeller.
With the twelfth feature, a gap between the turbine impeller and the boss of the stator impeller is sealed by the seal member. Therefore, it is possible to reliably inhibit the flowing-in and flowing-out of the oil through such gap to contribute to the prevention of reductions in torque ratio and transmitting efficiency.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.